On Wed, Nov 01, 2017 at 06:15:53AM -0500, Eric W. Biederman wrote: > Christian Brauner <christian.brau...@canonical.com> writes: > > > On Tue, Oct 31, 2017 at 06:46:32PM -0500, Eric W. Biederman wrote: > >> > >> Christian I have looked through your code and I have found one real > >> issue and of things I want to twak > > > > Cool, thanks for taking a close look Eric. > > > >> > >> The real issue is reading nr_extents multiple times when reading a map. > >> That can introduce races that will allow walking past the end of the > >> array, if the first read is 0 but the second read is > 5. > >> > >> I have also found a couple of tweaks that look like they are worth > >> implementing. > > > > Yeah, I saw that you unified some of the functions. I was thinking about > > this > > but wanted to keep the cases distinct even with some amount of code > > duplication. > > But it seems very much worth it from a maintenance perspective. Thanks! > > Yes. If we have a performance regression I am willing to remove the > unification of map_id_range_down and map_id_down. But I can't imagine > that will result in a measurable performance difference. If it does > make a measurable perforamnce difference we almost certainly need to split > the bsearch case as well. > > >> As all of these are very small and very straight forward I have > >> tested these and applied them all to my for-next branch > > > > Thanks for the fixes Eric. Really appreciated. If you're too swamped for > > stuff > > like that I'm obviously happy to do such trivial fixes myself. :) > > If you would test this some more in your setup I would appreciate it, > just in case I missed something.
I've been running kernels with this patch for a few weeks now with nested unprivileged containers and all sorts of weird setups. So far I didn't observe any problems. Once we've settled the memory barrier discussion I'm going to recompile and run a few tests. > > Given where we are in the development cycle and the correctness concerns > I just applied these as without the fix for reading extents exactly once > the code is dangerously wrong. > > Eric > > > Christian > > > >> > >> > >> Eric W. Biederman (5): > >> userns: Don't special case a count of 0 > >> userns: Simplify the user and group mapping functions > >> userns: Don't read extents twice in m_start > >> userns: Make map_id_down a wrapper for map_id_range_down > >> userns: Simplify insert_extent > >> > >> kernel/user_namespace.c | 159 > >> ++++++++++++++++-------------------------------- > >> 1 file changed, 51 insertions(+), 108 deletions(-) > >> > >> > >> > >>
